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DMEVENTD(8)                 System Manager's Manual                DMEVENTD(8)
NAME
       dmeventd -- Device-mapper event daemon
SYNOPSIS
       dmeventd [-d [-d [-d]]] [-e exit_on_path] [-f] [-h] [-i] [-l] [-R] [-V]
       [-?]
DESCRIPTION
       dmeventd is the event  monitoring  daemon  for  device-mapper  devices.
       Library  plugins can register and carry out actions triggered when par-
       ticular events occur.
OPTIONS
       -d     Repeat from 1 to 3 times (-d, -dd, -ddd) to increase the  detail
              of debug messages sent to syslog.  Each extra d adds more debug-
              ging information.
       -e exit_on_path
              Specifies the file path whose presence is checked by the  daemon
              when  it  receives a signal (SIGINT, SIGTERM) and allows to exit
              even if there are still monitored devices.  This can  help  with
              system  shutdown  where  devices have not been unmonitored prop-
              erly.  To disable this behavior set this to the empty string "".
              Default value is "/run/nologin".
       -f     Don't fork, run in the foreground.
       -h     Show help information.
       -i     Query  the  running daemon instance for the status informations.
              The format is internal and  unstable  and  it  is  targeted  for
              developers.  Format may change between versions.
       -l     Log  through  stdout  and stderr instead of syslog.  This option
              works only with option -f, otherwise it is ignored.
       -?     Show help information on stderr.
       -R     Replace a running dmeventd instance. The running  dmeventd  must
              be  version  2.02.77  or  newer.  The new dmeventd instance will
              obtain a list of devices and events to  monitor  from  the  cur-
              rently running daemon.
       -V     Show version of dmeventd.
LVM PLUGINS
       Mirror Attempts to handle device failure automatically.
              See lvm.conf(5).
       Raid   Attempts to handle device failure automatically.
              See lvm.conf(5).
       Snapshot
              Monitors  how full a snapshot is becoming and emits a warning to
              syslog when it exceeds 80% full.  The warning is  repeated  when
              85%,  90%  and  95% of the snapshot is filled.  See lvm.conf(5).
              Snapshot which runs out of space gets invalid  and  when  it  is
              mounted, it gets umounted if possible.
       Thin   Monitors  how full a thin pool data and metadata is becoming and
              emits a warning to syslog when it exceeds 80% full.  The warning
              is  repeated when more then 85%, 90% and 95% of the thin pool is
              filled. See lvm.conf(5).  When a thin pool fills over 50%  (data
              or  metadata) thin plugin calls configured dmeventd/thin_command
              with every 5% increase.  With default setting it calls  internal
              lvm  lvextend  --use-policies to resize thin pool when it's been
              filled above configured  threshold  activation/thin_pool_autoex-
              tend_threshold.  If the command fails, dmeventd thin plugin will
              keep retrying  execution  with  increasing  time  delay  between
              retries up to 42 minutes.  User may also configure external com-
              mand to support more advanced maintenance operations of  a  thin
              pool.  Such external command can e.g. remove some unneeded snap-
              shots, use fstrim(8) to free recover space in a thin  pool,  but
              also  can  use lvextend --use-policies if other actions have not
              released enough space.  Command is executed  with  environmental
              variable  LVM_RUN_BY_DMEVENTD=1  so any lvm2 command executed in
              this environment will not try to interact with dmeventd.  To see
              the fullness of a thin pool command may check these two environ-
              mental variables DMEVENTD_THIN_POOL_DATA and DMEVENTD_THIN_POOL_
              METADATA.  Command can also read status with tools like lvs(8).
       Vdo    Monitors  how full a VDO pool data is becoming and emits a warn-
              ing to syslog when it exceeds 80% full.  The warning is repeated
              when  more  then 85%, 90% and 95% of the VDO pool is filled. See
              lvm.conf(5).  When a VDO pool fills over 50%  vdo  plugin  calls
              configured  dmeventd/vdo_command  with  every 5% increase.  With
              default setting it calls internal lvm lvextend --use-policies to
              resize  VDO  pool  when  it's  been  filled above the configured
              threshold activation/vdo_pool_autoextend_threshold.  If the com-
              mand  fails,  dmeventd  vdo  plugin will keep retrying execution
              with increasing time delay between retries  up  to  42  minutes.
              User  may  also  configure  external  command  to  support  more
              advanced maintenance operations of a VDO  pool.   Such  external
              command  can e.g. remove some unneeded space with fstrim(8), but
              also can use lvextend --use-policies if other actions  have  not
              released  enough  space.  Command is executed with environmental
              variable LVM_RUN_BY_DMEVENTD=1 so any lvm2 command  executed  in
              this environment will not try to interact with dmeventd.  To see
              the fullness of a VDO pool command may check this  environmental
              variable  DMEVENTD_VDO_POOL.   Command can also read status with
              tools like lvs(8).
ENVIRONMENT VARIABLES
       DMEVENTD_THIN_POOL_DATA
              Variable is set by thin plugin and is available to executed pro-
              gram. Value present actual usage of thin pool data volume. Vari-
              able is not set when error event is processed.
       DMEVENTD_THIN_POOL_METADATA
              Variable is set by thin plugin and is available to executed pro-
              gram.  Value  present actual usage of thin pool metadata volume.
              Variable is not set when error event is processed.
       DMEVENTD_VDO_POOL
              Variable is set by vdo plugin and is available to executed  pro-
              gram.  Value present actual usage of VDO pool data volume. Vari-
              able is not set when error event is processed.
       LVM_RUN_BY_DMEVENTD
              Variable is set by thin and vdo  plugin  to  prohibit  recursive
              interaction  with  dmeventd  by any executed lvm2 command from a
              thin_command, vdo_command environment.
SEE ALSO
       lvm(8), lvm.conf(5), lvextend(8),
       fstrim(8)
Red Hat Inc         DM TOOLS 2.03.14(2)-RHEL8 (2021-10-20)         DMEVENTD(8)